In effect, it returned in an updated version with a chronograph mechanism with automatic winding from the Zenith workshop. In order to satisfy the Rolex specifications, whose after-sales service was governed by strict norms, the Zenith El Primero cal. 400 was adapted to oscillate at 28, 800 vibrations per hour and the date feature was withdrawn (the jumper was considered over-sensitive and prone to jumping erratically in older generations, namely those prior to the LVMH takeover in 2000). In practical terms, the crown manufacture made significant changes to the leading reference in calibres to satisfy the requirements and replaced over 50% of its components with parts specifically designed for its movements.
Rolex Oyster Perpetual Cosmograph Daytona from 1988

The resultant new calibre 4030 was thus equipped with an oscillator with variable inertia balance wheel and Microstella adjustment screws and a Breguet hairspring. The automatic winding module invented by the brand in 1931 replaced that of the initial calibre. The movement was submitted for official certification to earn the title of Chronometer, a guarantee of superior precision. The new model could now feature generally on the dial the words Oyster Perpetual Cosmograph Daytona, as well as the description: Superlative Chronometer Officially Certified.

The updated version of this model, however, went way beyond technical considerations. Its reworked aesthetics laid the foundations for the modern look of the Cosmograph Daytona, which exuded presence and elegance. Thus, the Oyster case went from 36 mm in diameter to an apparently under-sized 40 mm and acquired a protective shoulder for its crown. Moreover, the tachometer bezel was enlarged and engraved with a scale of graduations of up to 400 units per hour. The piece was also given new hands, new indices, the counters were circular-grained to lend the dial a more modern feel, without detracting from its inimitable style. Note also the choice of Daytona signature, present just above the elapsed hours counter, in red letters.

Source: www.watchonista.com

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